Baffle plate for annealing oven



Aug. 25, 1964 M. LUDWIG Filed March 19, 1962 2 Sheets-Sheet 1 I H v 3 1 4 fiH/ Matthias LUDWIG INVENTOR.

BY (Karl i298;

AGENT Aug. 25,1964 M. LUDWIG 3,145,982

' I BAFFLE PLATE FOR ANNEALING OVEN Filed March'lQ, 1962 2 Sheets-Sheet 2 21 i 3 I '15 'A hot I J g gas 1 20 ?3/ 23 I I! I u FIG. 3

I I Matthias LUDWIG I! INVENTOR.

BY Gaul ja AGENT United States Patent a com any of Germany Filed Mar. 19, 1962, Ser. No. 180,474 Claims priority, applicaltlioziis, SGSrmany, Mar. 25, 1961,

4 Claims. 61. 263-47) My present invention relates to a baffle plate for supporting stacked objects, especially rolls of coiled sheet metal, in an annealing oven within which a suitable heating fluid such as a non-oxidizing gas is circulated.

It is known to support and separate such objects by means of centrally apertured baflle plates having radially or spirally disposed ribs between which there exist convection channels for the passage of the gas toward a central shaft defined by the aligned apertures. A major problem in the design of such plates has heretofore been the shaping of their ribs and channels in such a way that the gas could circulate freely and give off its heat to the adjacent objects while affording sufiiciently wide contact surfaces between the ribs and the objects to prevent undesirable deformations. In the case of coiled sheets, for example, ribs with unduly narrow edges may cut into the edges of the sheet, which (unless of relatively great thickness) is particularly susceptible to deformation in view of the high temperatures prevailing within the oven, and may cause fusion between adjoining turns of the coil.

It is, therefore, an important object of my invention to provide a bafiie plate for the purpose set forth which, while being itself resistant to thermal warping or bending under load and at high temperatures, offers a sufficiently large supporting surface to avoid any objectionable deforming of the edges of sheet-metal coils or similar objects while offering virtually unobstructed passage to gas currents flowing inwardly along these plates.

Another object of the invention is to provide a bafile of the aforestated type in which the ribs and channels are so designed as to protect the outer periphery of the diskshaped plate body from overheating While insuring substantially uniform distribution of the gas flow.

In accordance with an important feature of this invention I provide a bafie plate whose centrally apertured disk-shaped body is preferably integrally formed with ribs of generally triangular configuration converging toward its aperture, the ribs being advantageously coextensive on opposite disk faces and terminating substantially at the rim of the aperture while projecting beyond the outer periphery of the disk.

The ribs are bounded, in accordance with a major feature of the invention, by sides extending along lines which are tangent to different circles within the circumference of the central aperture and offset in the same direction from its center, the direction of offset being so chosen that the gas streams entering the central aperture through the channels are given a spin in a sense which advantageously coincides with the sense of their external circulation. The ribs may be in the shape of right triangles, with a long leg and the hypotenuse of the triangle tangent to the aforementioned circles and with a short leg forming an edge outside the periphery of the disk, the spacing of the latter edge from the disk periphery ranging preferably between about one-fourth and one-fifth of the length of the rib. By this means the periphery of the disk is set back from the outer ends of the ribs to such an extent that exposure of the disk periphery to the externally circulating hot gases is minimized as the objects to be heated overlie this periphery; the projecting parts of the ribs act, in effect, as temperature-equalizing fins in addition to de- 3,145,982 Patented Aug. 25, 1964 fining the entrances to the convection channels. I have also found that favorable flow conditions are realized if the width of each channel tapers from its entrance to its exit and (next to the central aperture) at a rate of about 2:1.

The invention will be described in greater detail with reference to the accompanying drawing in which:

FIG. 1 is a top plan view of a baifie according to the invention;

FIG. 2 is a cross-sectional view taken on line IIII of FIG. 1; and

FIG. 3 is a perspective view (parts broken away) of an annealing oven incorporating a set of baflle plates of the type shown in FIGS. 1 and 2.

The plate 20 shown in FIGS. 1 and 2 is one of several disposed within an annealing oven 21, FIG. 3, in which these plates serve as partitions between stacked coils 22 of sheet metal. The oven 21 is shown as a cylindrical hood which surrounds the stack 20, 22 and may be lifted off by a crane; the coils 22 and bafile plate 20 may also be placed in position or removed from the stack by crane action, e.g. electromagnetically. Heated gas is ad'- mitted with a tangential velocity component into the oven 21 at one or more periphery locations, as shown at 23, in such manner that a clockwise circulation is established therein as indicated by the arrows 24 in FIGS. 1 and 3. Each plate 20 has a disk-shaped body 4 formed with a central aperture 3, these apertures registering with the bores 25 of the coils 22 whereby a vertical air shaft is formed at the center of the stack. Channels I extend along both faces of each baffle plate 20, these channels being defined by the major edges 9, 10 of the coextensive upper and lower ribs 5 integral with the disk 4. The ribs 5 project beyond the outer periphery of disk 4 for a distance corresponding to approximately one-fourth to one-fifth of their length; the coils 22, in turn, have a diameter substantially equal to that of the disk 4 so as to be spaced from the short outer edges 8 of the ribs 5. The gas swirling around the stack 20, 22 can thus pass inwardly into the shaft 3, 25 through the channels 1 as indicated by the arrows 2 in FIG. 2. This hot gas tends to rise on the outside of the stack, i.e. between the projecting rib portions and around them to the extent that clearance exists between the edges 8 and the wall of oven 21, and to descend within the shaft 3, 25 as its temperature decreases because of its heat exchange with the stack. The relatively cool spent gas exits at 26.

The channels 2 are so offset from the radial direction of the disks 4 that the gas streams entering the shaft 3, 25 are set into swirling motion so that the column of gas within the shaft rotates in the same sense as the gas sheath enveloping the stack, i.e. clockwise as indicated by the arrow 27. To this end the long edges 9 and 10 of the ribs 5 extend along lines which are offset from the center of the disk 4- and are tangent to two circles 29, 30, respectively, both concentric with and located within the circumference of the central disk aperture 3. The centerline 28 of each channel 1 is shown to intercept at the channel mouth (i.e. at the rim of aperture 3) a radius 6 which includes with this centerline an angle o of approximately 30. The width of the channel is shown to decrease by a factor of two from the channel entrance at 2 to the channel exit at 3.

The edges 9 and 10 of the ribs 5 constitute, respectively, the hypotenuse and the long leg of a right triangle whose short leg is the edge 8 and whose right angle is located at the somewhat rounded corner 7.

The shaping of the ribs 5 and the tapering of the channels 1 described above promote the establishment of flow conditions favorable to an intense heat exchange, including particularly the occurrence of turbulent flow. Since the average width of the channels is somewhat less than that of the ribs, good broadside support is offered to the coils 22 and deformation of the relatively thin web constituting the disk body 4 is prevented.

Departures from the specific structures described and illustrated are, of course, possible within the scope of the invention as defined in the appended claims.

I claim:

1. A supporting baffie for annealing ovens, comprising a metallic disk with a circular central aperture having integral ribs coextensively disposed on opposite faces thereof, said ribs being of generally triangular configuration with converging sides extending along lines tangent to different circles within the circumference of said aperture and offset in the same direction from the center of said aperture, said ribs being separated by channels narrowing toward said aperture whereby the width of said channels at said aperture is substantially half their width near the outer periphery of said disk.

2. A bafile according to claim 1 wherein each of said ribs is provided in the region of said periphery with an outer edge substantially perpendicular to that one of said lines which is closer to said center.

3. A baffle according to claim 1 wherein said channels each have a centerline which includes an angle of about 30 with a disk radius intercepting said centerline at the inner end of the channel.

4. A supporting baffie for annealing ovens, comprising a metallic disk with a circular central aperture having integrally formed ribs coextensively disposed on opposite faces thereof, said ribs being of generally triangular configuration with converging sides extending along lines tangent to different circles within the circumference of said aperture and ofiset in the same direction from the center of said aperture, said ribs terminating substantially at said circumference while projecting beyond the outer periphery of said disk, each of said ribs being provided in the region of said periphery with an outer edge substantially perpendicular to that one of said lines which is closer to said center, said edge being positioned beyond said periphery by a distance ranging between approximately one-fourth and one-fifth of the length of the rib, said ribs being separated by channels narrowing toward said aperture at such rate that the width of each channel in the region of said edge is substantially twice its width at said circumference, each of said channels having a centerline which includes an angle of about 30 with a disk radius intercepting said centerline at said circumference.

References Cited in the file of this patent UNITED STATES PATENTS 1,453,411 Smail May 1, 1923 2,671,656 Winder Mar. 9, 1954 2,981,530 Menough Apr. 25, 1961 2,998,236 Cramer et al Aug. 29, 1961 2,998,967 Dailey et a1. Sept. 5, 1961 3,039,754 Jones June 19, 1962 FOREIGN PATENTS 1,156,390 France May 14, 1958 

1. A SUPPORTING BAFFLE FOR ANNEALING OVENS, COMPRISING A METALLIC DISK WITH A CIRCULAR CENTRAL APERTURE HAVING INTEGRAL RIBS COEXTENSIVELY DISPOSED ON OPPOSITE FACES THEREOF, SAID RIBS BEING OF GENERALLY TRIANGULAR CONFIGURATION WITH CONVERGING SIDES EXTENDING ALONG LINES TANGENT TO DIFFERENT CIRCLES WITHIN THE CIRCUMFERENCE OF SAID APERTURE AND OFFSET IN THE SAME DIRECTION FROM THE CENTER OF SAID APERTURE, SAID RIBS BEING SEPARATED BY CHANNELS NARROWING TOWARD SAID APERTURE WHEREBY THE WIDTH OF SAID CHANNELS AT SAID APERTURE IS SUBSTANTIALLY HALF THEIR WIDTH NEAR THE OUTER PERIPHERY OF SAID DISK. 